All single-chip integrated circuit devices that require clock signals require a clock source to provide the clock signals. The mainstream clock sources have an off-chip crystal oscillator, an on-chip harmonic oscillator, an on-chip ring oscillator and an on-chip relaxation oscillator. The crystal oscillator is widely used due to its favorable frequency accuracy and stability. With the development of Internet-of-Things devices, wearable devices and medical implantable devices, the market's demand for the integratability of electronic devices is higher and higher, the requirement on power dissipation control is increasingly rigorous, and the desire for cost reduction is stronger and stronger. Hence, the performance of an on-chip integratable oscillator needs to be improved substantially to replace the crystal oscillator and to meet the increasingly higher market demand. The relaxation oscillator is widely used and studied for its low power dissipation, easiness in frequency control and simple structure.